3D Structure and Nuclear Targets

TL;DR

This paper discusses recent experimental and theoretical advances in understanding the three-dimensional parton structure of nuclei, focusing on exclusive processes and semi-inclusive scattering to reveal spatial and momentum distributions of partons.

Contribution

It introduces new approaches using generalized parton distributions and transverse momentum dependent distributions to explore nuclear structure beyond inclusive scattering.

Findings

3D parton distributions can be accessed via exclusive and semi-inclusive processes.

Experimental measurements at Jefferson Laboratory are advancing the field.

Future facilities will enhance the understanding of nuclear parton structure.

Abstract

Recent experimental and theoretical ideas are laying the ground for a new era in the knowledge of the parton structure of nuclei. We report on two promising directions beyond inclusive deep inelastic scattering experiments, aimed at, among other goals, unveiling the three dimensional structure of the bound nucleon. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-perturbative content is parametrized in terms of generalized parton distributions. In this way the distribution of partons in the transverse plane will be obtained, providing a pictorial view of the realization of the European Muon Collaboration effect. In particular, we show how, through the generalized parton distribution framework, non nucleonic degrees of freedom in nuclei can be unveiled. Analogously, the momentum space 3D structure can be accessed by studying transverse momentum dependent parton distributions in semi-inclusive deep inelastic scattering processes. The status of measurements is also summarized, in particular novel coincidence measurements at high luminosity facilities, such as Jefferson Laboratory. Finally the prospects for the next years at future facilities, such as the 12~GeV Jefferson Laboratory and the Electron Ion Collider, are presented.